The subject matter disclosed herein relates to an airfoil having a cooling hole with a flag region.
In turbine engines, such as gas turbine engines or steam turbine engines, fluids at relatively high temperatures contact blades that are configured to extract mechanical energy from the fluids to thereby facilitate a production of power and/or electricity. While this process may be highly efficient for a given period, over an extended time, the high temperature fluids tend to cause damage that can degrade performance and increase operating costs.
Accordingly, it is often necessary and advisable to cool the blades to at least prevent or delay premature failures. This can be accomplished by delivering relatively cool compressed air to the blades. In many traditional gas turbines, in particular, this compressed air enters the bottom of each of the blades and flows through one or more round machined passages in the radial direction to cool the blade through a combination of convection and conduction.
In these traditional gas turbines, as the temperature of the fluids increase, it becomes necessary to increase the amount of cooling flow through the blades. This increased flow can be accomplished by an increase in a size of the cooling holes. However, as the cooling holes increase in size, the wall thickness of each hole to the external surface of the blade decreases and eventually reaches a minimum wall thickness required to maintain manufacturability and structural integrity of the blade.